Over the course of the past decades, mechanical heart support systems have become more and more prevalent as a therapeutic method for treating chronic cardiac insufficiency. Their main task consists of maintaining blood circulation, thus ensuring an adequate supply of oxygen to organs and tissues in cases of heart failure. More recent developments in the realm of mechanical circulatory support systems have led to the creation of numerous pump mechanisms which, depending on the clinical indication, range from unilateral ventricular assist devices (VAD) to total heart replacement or artificial heart (TAH) systems. It is common knowledge in the realm of heart surgery nowadays that the clinical demand for ventricular assist devices is considerably higher than the demand for total artificial heart systems, and left-ventricular assist devices (LVAD) are of special significance due to the higher hemodynamic load on the left half of the heart. A major therapeutic objective of an assist device is to provide a “bridge-to-transplant”, wherein the VAD system takes over or assists the pumping capacity of the insufficient heart until a suitable donor organ becomes available and a heart transplantation can be performed. According to pertinent statistics, approximately 70% of the patients with mechanical assist systems reach the stage of heart transplantation, which is then performed with a mortality rate of less than 10% (Hammel et al., Mechanische myokardiale Unterstützungsysteme [Mechanical myocardial assist systems] 1997, published in the journal Anaesthesist, No. 46, pages 408-418, 1997). A more in-depth treatment of the clinical and technical aspects and special features of VAD and TAH systems has been provided by Akdis et al. (Handbuch der Kardiotechnik [Manual of cardiotechnology], 4th Edition, pages 461-482, published by Urban & Fischer Verlag, 2002), and by Hetzer et al. [Kardiale Assist-Systeme: Gegenwärtiger Stand [Cardiac assist systems: current status] in the journal Herz, No. 5, pages 407-417, published by Urban & Fischer Verlag, 2002).
German publication DE 698 28 962 T2 discloses a blood pump with an impeller. Here, the blood pump has an inlet and an outlet. In this blood pump, the impeller is radially supported by two magnetic bearings. Moreover, the impeller is stabilized in the radial direction by a hydrodynamic bearing in the form of raised surfaces and contact surfaces. When the impeller turns, these hydrodynamic bearings cause the impeller to be separated from the housing by means of a liquid film. The functionality of this hydrodynamic bearing is based on constricted bearing gap geometries that are formed by several bearing elements whose shape is rectangular or tapered.